In general, in a memory system such as an SSD (Solid State Drive), write data requested to write by a host is written into nonvolatile memory. In the memory system at this time, the write data is written into the nonvolatile memory via volatile memory such as a buffer.
Even in a case where sudden power shut down has occurred, in such a memory system, it is necessary in some cases to store write data for which a response of write completion is given to a host, into nonvolatile memory. In the memory system, therefore, data in volatile memory is written into nonvolatile memory by using a backup battery.
In a case where large power is used at the time of writing, however, the backup battery becomes large in size and high in cost. Therefore, it is desired to reduce the size and cost of the backup battery by making write data nonvolatile with low power when sudden power shut down has occurred.